Supporting device for a vibration driven actuator

ABSTRACT

A planar auxiliary supporting member for supporting an elastic member for generating a vibration is arranged. The elastic member contacts a rail-shaped stationary member, and moves along the stationary member. The rigidity of the supporting member is set to be low, so that the elastic member as a stator stably moves along the stationary member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vibration wave motor and, moreparticularly, to a vibration wave motor wherein an elastic member inwhich a travelling wave is generated is urged against a rail-likestationary member, and is moved along the rail-like stationary member,and to a printer using the vibration wave motor.

2. Description of the Related Art

A conventional vibration wave motor of this type is proposed in U.S.Pat. No. 5,192,890. FIGS. 11 and 12 show the motor.

An elastic member 1 consists of a metal material, and has a projection1a formed on the sliding surface side. When an AC voltage is applied toa piezoelectric element 2 joined to the upper surface of the elasticmember 1, a travelling vibration wave is generated in the elasticmember 1. Since the generation principle of the travelling vibrationwave and the structure of the piezoelectric element 2 are known to thosewho are skilled in the art, a detailed description thereof will beomitted. Generally, the travelling vibration wave is formed when ACvoltages having a temporal phase difference of 90° are applied to twogroups of driving piezoelectric elements which are positionally shiftedby 90° of the piezoelectric element. A rail-shaped stationary member 8frictionally contacts the elastic member 1, and is fixed to a bottomplate 10 of a motor case. More specifically, the elastic member 1 isbiased to contact the stationary member 81 via a vibration insulatingmember 6 (e.g., felt) and a compression spring 3.

A planar auxiliary supporting member 7 has an H shape when it is viewedfrom the top (see, e.g., FIG. 12), and is joined to the bottom portionof a slit of the elastic member 1. The supporting member 7 firmlysupports the central portion of the elastic member 1 to a table 4. Thus,the elastic member 1 can make a smooth linear motion together with thetable 4 without cluttering.

This motor is used for driving a printing head in, e.g., a bubble-jetprinter. The printing head is mounted on a carriage (not shown) attachedto the table 4, and the motor linearly and reciprocally moves theprinting head.

However, it is very difficult to accurately bring the elastic member 1into surface-contact with the rail-shaped stationary member 8 due todimensional errors of parts, and the like. In practice, as shown inFIGS. 13 and 14, the elastic member 1 may contact the stationary member8 at an oblique angle. For this reason, the contact state between theelastic member 1 and the rail-shaped stationary member 8 becomes linecontact and unstable. When the contact state changes in the movingdirection of the elastic member 1, it is difficult to stably move theelastic member 1.

Such problems of the vibration wave motor impair print precision of theprinter.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a vibration wavemotor which can stably move an elastic member.

It is another object of the present invention to provide a printerapparatus which can realize high-precision printing.

Other objects of the present invention will become apparent from thefollowing detailed description of the present invention.

In one aspect, a planar auxiliary supporting member for supporting anelastic member for generating a vibration is arranged. The elasticmember contacts a rail-shaped stationary member, and moves along thestationary member. The rigidity of the supporting member is set to below, so that the elastic member as a stator stably moves along thestationary member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing the first embodiment of the presentinvention;

FIG. 2 is a side view showing the use state of FIG. 1;

FIG. 3 is a side view showing the second embodiment;

FIG. 4 is a side view showing the third embodiment;

FIG. 5 is a plan view showing principal parts of FIG. 4;

FIG. 6 is a perspective view showing the fourth embodiment;

FIG. 7 is a side view of FIG. 6;

FIG. 8 is a side view showing the fifth embodiment;

FIG. 9 is a plan view of FIG. 8;

FIG. 10 is a perspective view showing an embodiment of a printerapparatus using a vibration wave motor according to the presentinvention;

FIG. 11 is a side view of a conventional vibration wave motor;

FIG. 12 is a plan view of FIG. 11;

FIG. 13 is a side view showing the use state of the vibration wave motorshown in FIG. 11; and

FIG. 14 is a side view showing the use state of the vibration wave motorshown in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail hereinafter withreference to illustrated embodiments. The same reference numerals denotethe same parts as in the prior art, and a detailed description thereofwill be omitted. Since a method of generating a travelling wave in atrack type vibration member is known to those who are skilled in theart, a description thereof will be omitted as well.

FIG. 1 shows the first embodiment of the present invention.

In this embodiment, an elastic member 1 has an elliptical shape, asshown in FIG. 12, and has a plurality of projections defined by aplurality of grooves on a portion contacting a rail-shaped stationarymember 8. The entire width, from an outer circumferential portion 1AA toan inner circumferential portion 1AB, of a single straight portion ofthe elastic member 1 contacts the rail-shaped stationary member 8.Furthermore, in order to uniformly distribute compression between thestationary member 8 and the elastic member 1, a compression plate 5 isarranged between a felt 6' and a compression spring 3', and a projection3'a of the compression spring 3' is formed at a position where thecompression force acts on the central portion, in the widthwisedirection, of the compression plate 5.

Note that the projection 3'a is formed by bending a portion of thespring 3'.

Note that FIG. 1 illustrates a case wherein the respective parts haveideal dimensional precision. For example, when the dimensional precisionis low, and the position of the elastic member 1 is shifted upward inFIG. 1, a planar auxiliary supporting member 7 flexes, as shown in FIG.2. At this time, when the counterforce of the supporting member 7 is setto be equal to or lower than half a compression force of the compressionspring 3', almost the entire contact surface of the elastic member 1contacts the contact surface of the rail-shaped stationary member 8, andthe posture of the elastic member 1 follows the frictional surface ofthe rail-shaped stationary member 8. Therefore, the counterforce of theplanar auxiliary support member 7 influences the compressiondistribution unless its rigidity is set to be considerably lower thanthat of the compression spring 3'.

FIG. 3 shows a second embodiment of the present invention. In thisembodiment, two portions, i.e., an outer peripheral portion 1b and aninner peripheral portion 1c of a single straight portion of the elasticmember 1 contact the rail-shaped stationary member, so that the postureof the elastic member 1 follows the frictional surface of therail-shaped stationary member 8. The two contact portions need only beseparated by a certain distance, and need not always be located at theoutermost and innermost peripheral positions.

FIGS. 4 and 5 show a third embodiment of the present invention. In thisembodiment, a planar auxiliary supporting member 70 is joined to onlyone straight portion of the elastic member 1. Thus, the planar auxiliarysupporting member 70 has considerably lower rigidity than that in thefirst and second embodiments, and does not adversely influence thecompression distribution.

In this embodiment, a distal end portion 70a (see FIG. 5) of the planarauxiliary supporting member 70 is joined to the bottom portion of theslit of the elastic member 1. The position of the joint portion isdesirably set at or near the middle point between adjacent antinode andnode of two standing waves (wavelength λ) which are shifted from eachother by λ/4, as described in Japanese Laid-Open Patent Application No.4-21374.

FIGS. 6 and 7 show a fourth embodiment of the present invention. FIG. 6illustrates only the planar auxiliary supporting member 71. In thisembodiment, projected portions 71a are formed by bending the distal endsof the supporting member, and are joined to the inner side surface ofthe elastic member 1, as shown in FIG. 7.

FIGS. 8 and 9 show a fifth embodiment of the present invention. A pairof projected portions 1d are formed on the side surface of an innercircumferential portion of the elastic member 1, and distal end portions72a of a planar auxiliary supporting member 72 are joined to theprojected portions 1d. Note that the projected portions 1d formed on theelastic member 1 are arranged near the neutral surface of the elasticmember 1 so as not to disturb the vibration of the elastic member 1.

In the above embodiments of the present invention, the planar auxiliarysupporting member 7 has an H shape, and the members 70 (FIG. 4), 71(FIG. 6), and 72 (FIG. 8) have corresponding shapes. However, thepresent invention is not limited to these shapes. For example, thesupporting member may have an X shape, as disclosed in JapaneseLaid-Open Patent Application No. 4-21374.

Also, in the above embodiments, the projection 1a, or the projections 1band 1c of the elastic member 1 directly contact the rail-shapedstationary member 8. Alternatively, a resin may be adhered, as a slidingmember, to the projection 1a of the elastic member 1, or the projections1b and 1c in FIG. 3 may be formed using a resin. In each of the aboveembodiments, the elastic member 1 moves along the rail-shaped stationarymember 8. Alternatively, the elastic member 1 may be fixed, and amovable member may move along the elastic member.

FIG. 10 is a perspective view of a bubble-jet printer apparatus usingthe above-mentioned vibration wave motor. A printing head 29 is placedon a carriage 40 to eject an ink, and the ejected ink is printed on apaper sheet 20 fed by a paper feed vibration wave motor 1' (as disclosedin, e.g., Japanese Laid-Open Patent Application No. 3-31137). A slitplate 24 for forming an encoder is arranged to control the feed speed ofthe carriage, and a rotary encoder 21 for detecting the paper feedamount is rotated by a roller 22 urged against the upper surface of thepaper sheet 20.

As described above, according to the present invention, since theauxiliary supporting member has low rigidity, the posture of the elasticmember follows the frictional surface of the rail-shaped stationarymember. Thus, the contact state between the elastic member and thestationary member can be stabilized, so that the elastic member canstably move.

If the slit bottom surface of the elastic member has good flatness, thenthe planar auxiliary supporting member is preferably joined to thissurface for the purpose of easy manufacture. When the slit bottomsurface does not have good flatness, the supporting member may be joinedto the side surface of the elastic member, or maybe joined to aprojected portion formed on the side surface of the elastic member so asto facilitate a joint process.

When the above-mentioned vibration wave motor is utilized as a drivesource for driving, e.g., a printing head, high-precision printing canbe realized.

What is claimed is:
 1. A vibration driven apparatus, comprising:astationary member having a contact surface; comprising: a stationarymember having a contact surface; a vibration generating member, having acontact surface contactable with the contact surface of said stationarymember; an elastic supporting member provided on said vibrationgenerating member; and a pressing member for biasing said stationarymember and said vibration generating member in a press contact state,wherein said vibration generating member moves relative to saidstationary member by a vibration of said vibration generating member,and wherein said elastic supporting member includes means for exerting aforce on said vibration generating member less than a force the pressingmember exerts on the vibration generating member.
 2. A vibration drivenapparatus according to claim 1, wherein said supporting member isplanar.
 3. A vibration driven apparatus according to claim 1, whereinsaid vibration generating member is elliptic.
 4. A vibration drivenapparatus according to claim 3, wherein said pressing member has aprojecting portion, which presses the vibration generating member, sothat the vibration generating member is in press contact with thestationary member.
 5. A vibration driven apparatus according to claim 3,wherein said pressing member has a projecting portion, which presses acentral area of the vibration generating member, so that the vibrationgenerating member is in press contact with the stationary member.
 6. Avibration driven printing device, comprising:a stationary member havinga contact surface; a vibration generating member, having a contactsurface contactable with the contact surface of said stationary member;an elastic supporting member provided on said vibration generatingmember; a pressing member for biasing said stationary member and saidvibration generating member in a press contact state, wherein saidvibration generating member moves relative to said stationary member bya vibration of said vibration generating member; and a printing headmovable with a movement of said vibration generating member in aninterlocking manner; wherein said elastic supporting member includesmeans for exerting a force on said vibration generating member less thana force the pressing member exerts on the vibration generating member.7. A vibration driven printing device according to claim 6, furthercomprising:a guide member for movably holding said printing head.